This invention relates to intravenous administration sets, and more particularly, relates to an inline accumulator tube for use in intravenous administration sets to accumulate and store the fluid being administered when flow stoppage or restriction occurs downstream of the accumulator tube.
In gravity feed intravenous administration sets, there is a common problem of intermittent stoppage or restriction of flow of fluid through the intravenous administration set. This intermittent or temporary stoppage or restriction of flow is attributed to various factors, such as the needle or cannula pressing against the wall of the vein or rolling over of the patient or other occurrences which impose a back pressure on flow through the system resulting in a reduction of the flow rate. This momentary stoppage or slowdown of the flow reduces the intended volume of fluid to be delivered to the patient, and in many intravenous administration control means, as shown, for example, in U.S. Pat. Nos. 3,890,968, 3,790,042 and 3,655,095, this momentary blockage of flow results in an error signal being generated with the result that the control means is disrupted. This generally requires the attention of an attendant and, additionally, necessitates that the volume of fluid not delivered during the period of blockage must be made up.
The present invention provides a unique and simple solution to the problems encountered in prior art gravity feed devices. In accordance with the invention, an expansible chamber or accumulator tube is provided inline in the intravenous administration set such that a temporary blockage or restriction of flow through the set causes the fluid being delivered to expand the accumulator tube and be collected or stored therein for subsequent delivery to the patient when the blockage or restriction is removed. Thus, the invention ensures that the proper volume of fluid is delivered to a patient and prevents various electronic control means, as disclosed in the above-noted patents, for example, from entering an alarm mode when temporary blockage or stoppage occurs. In fact, the temporary blockage or restriction of flow through an intravenous administration set normally corrects itself and the accumulated fluid in the expansible chamber is delivered to the patient without requiring any action on the part of an attendant or the like. The invention thus reduces or eliminates errors in volume of fluid administered and also solves the problem of attempting to catch up with delivery of a predetermined volume of fluid when a flow blockage or restriction has occurred.
In order to ensure that an excessive volume of fluid is not stored for subsequent rapid delivery to the patient, means is provided in association with the expansible accumulator tube to limit the expanded volume thereof to a predetermined safe amount. Thus, the invention is constructed to accumulate for subsequent delivery to the patient only those amounts of fluid which would normally be missed during normal flow blockage or stoppage of a temporary nature. In other words, if the flow blockage or restriction is permanent in nature, or more serious than a temporary stoppage of the type discussed hereinabove, then once the volume of the accumulator tube has been reached, the control means controlling delivery of the intravenous fluid will enter alarm.